This invention relates generally to clamping devices, and more particularly to adjustable, low-profile toe clamping devices for holding a workpiece.
Low-profile toe clamps are used by machinists and manufacturers to hold workpieces or stock, such as aluminum, steel, brass, etc., that will be machined into a product or component of a product. A workbed, fixture plate, or similar device is designed to accept the workpieces and toe clamps in order to hold the workpieces in place while machining occurs.
Toe clamps secure the workpiece to a fixture plate with downward and inward force so as to prevent relative movement. This securing is important for both safety and accuracy. If the workpiece moves during the machining process, the workpiece may be rendered useless due to incorrect tolerances. The workpiece may also become unclamped if the clamping system fails.
There are several machine clamps disclosed in the prior art. One is U.S. Pat. No. 2,587,025 issued Feb. 26, 1952 to G. H. Beck et al. for WORK CLAMP. Another is U.S. Pat. No. 4,805,888 to Bishop for ORBITAL-ACTION CLAMPS.
Beck appears to disclose a rocking clamp with an abutment bolted to a work surface. The abutment forms an acute angle relative to the work surface. The clamp has arcuate bottom corner which is contained in the acute angle between the abutment and the work surface. As the clamp rotates relative to the abutment block, an upward force is created on the abutment block. This force may cause the bolts holding the abutment block to the work surface, or another part of the Beck system, to fail. Beck also appears to rely on a slot in the work surface in order to accommodate horizontal displacement of the clamp during the tightening process.
Bishop discloses orbital-action clamps for securing a workpiece. The clamp has a head portion in rotatably eccentric independent motion from a base portion. The eccentric motion of the head causes flat surfaces about the periphery of the clamp to engage the workpiece. The Bishop disclosure uses eccentric horizontal motion to engage a surface.
One object of the invention is to provide a low-profile clamping device.
Another object of the invention is to provide greater clamping force.
And another object of the invention is to provide a low-profile clamping device which provides a substantial vertical, as well as horizontal, clamping force.
And another object of the invention is to provide a clamping apparatus generating sufficient force to hold a workpiece using fewer clamps, thereby reducing material and set-up costs.
Still another object of the invention is to provide clamping devices which can be incorporated into existing fixtures or work jaws.
Yet another object of the invention is to provide a clamping system with a one-piece fixture base or a multi-piece fixture base.
And another object of the invention is to provide a clamping apparatus having predictable and accurate contact, parallelism, and clamping force with the workpiece.
And another object of the invention is to provide a clamping apparatus which may be used with a standard screw.
And still another object of the invention is to provide a clamping apparatus having a high degree of safety.
These and other objects of the invention are addressed by the present invention, which comprises a clamp for securing a workpiece to a support. The invention includes the rocking clamp having, on opposed ends, a vertical arcuate edge and a workpiece-engaging edge. The vertical arcuate edge is rotatably held by the support at a vertical, and a horizontal, contact point. The rocking clamp contains a substantially vertical hole located between the arcuate edge and the workpiece-engaging edge. The hole is sized to allow a middle portion of the shank of a screw to non-threadably pass through the rocking clamp. The hole is also elongated in the direction of an axis from the vertical arcuate edge to the workpiece-engaging edge.
A jacking screw is inserted through the hole in the rocking clamp to threadably engage the support. As the jacking screw is tightened into the support, the head of the screw engages the rocking clamp. This causes the vertical arcuate edge to rotate and the engaging edge to secure the workpiece. The workpiece may be removed after loosening the screw.
In one embodiment, the support is configured with the horizontal contact point of the arcuate edge at a level below the bottom of the workpiece.
In another embodiment, the support is configured with the horizontal contact point of the arcuate edge at the same level as the bottom of the workpiece.
In yet another embodiment, the support is configured with the horizontal contact point of the arcuate edge at a level above the bottom of the workpiece.
In one form of the invention, the vertical arcuate edge has a circular radius and rotates about a particular point.
In another form of the invention, the vertical arcuate edge has an elliptical radius and rotates about a moving center.
In one form of the invention, the workpiece-engaging edge may be a knife edge, an angled edge, a serrated edge, a straight edge, or an arcuate edge, and/or may be coated with urethane, rubber, industrial diamond, polymer or a hardened material.
In another form of the invention, the workpiece-engaging edge is a machinable jaw. A removable pin is provided to secure the rocking clamp for machining the jaw.
In one embodiment, the elongated hole is slightly radiused at the shoulder portion between the jacking screw and the rocking clamp.
In a preferred embodiment, the elongated hole is counter-bored to substantially contain the head of the jacking screw within the rocking clamp.
In still another embodiment, a spherical washer is configured annularly about the jacking screw between the head of the jacking screw and the rocking clamp.
In yet another embodiment, an O-ring is configured annularly about the jacking screw between the rocking clamp and the supporting surface.
In yet another embodiment, gripping parallels secure a workpiece on a magnetic surface.
In another embodiment, a spring is configured annularly about the jacking screw between the rocking clamp and the supporting surface.
In an embodiment, the rocking clamp is surrounded by a urethane skirt.
In another embodiment, the rocking clamp is encapsulated in a resilient material.
In still another embodiment, a fixture base with a clamp trough contains one or more rocking clamps.
In another preferred embodiment, an automatic clamping system is disclosed.
In one preferred embodiment, the rocking clamp may be formed out of brass, bronze, steel, carbide, ceramics, plastic and the like.